Production of twist lively thread



ly 1961 B. VAN DEN BERGH ETAL 2,993,333

PRODUCTION OF TWIST LIVELY THREAD Filed July 13, 1956 INVENTORS ATTORNEY United States Patent 2,993,333 PRODUCTION OF TWIST LIVELY THREAD Barend van den Bergh and Cornelis Jan Stadig, Arnhem, Netherlands, assignors to American Enka Corporation, Enka, N.C., a corporation of Delaware 7 Filed July 13, 1956, Ser. No. 597,659 'Claims priority, application Netherlands July 19, 1955 2 Claims. (6]. 57157) This invention relates to the production of twist lively threads of linear polycondensation products for knitting and more particularly to a method for the continuous production of threads characterized by twist liveliness and easy knittability.

In the manufacture of novelty or special effect yarns from linear polycondensation products the threads are drawn, submitted to a heat treatment and twisted. Threads so processed are usually intended to be incorporated in knit goods and the improved properties of the thread are for the purpose of improving the elasticity of the final product. Heretofore the drawing, heat treatment, and twisting have been carried out as completely separate operations, that is to say, after drawing, the threads are collected in package form, submitted to heat treatment and exposed to the action of moisture or a hydroxy compound. After this treatment the threads are twisted to such a degree that they have twist liveliness which improves the elasticity of knit goods in which they are used. Since twist liveliness is a desirable property in the knit goods, but not during the knitting, it is common to suppress twist liveliness by a sizing or a moderate heat treatment and then to restore it after the knitting operation has been completed.

It is an object of the present invention to improve upon the foregoing processes and to produce a twist lively yarn characterized by easy knittability without twist suppression.

It is proposed according to the present invention continuously and successively to draw, dry heat, cool, and ring twist succeeding lengths of a monofil of a linear polycondensation product and then to impart twist liveliness by greatly increasing the twist of the already twisted monofil. Suprisingly enough, the resulting monofil is characterized by easy knittability without the use of sizing or a heat treatment and yet the twist liveliness apparent in the knit product is extremely good.

Other objects and advantages of the present invention will be apparent upon consideration of a specific embodiment thereof in conjunction with the annexed drawings wherein the single figure is a schematic representation of the continuous draw and heat treatment process and apparatus according to the teachings of the present invention.

In the drawing, a production type polycaprolactam monofil, which is substantially undrawn and substantially untwisted, is fed from a source, not shown, between a driven supply roller 10 and an idling pressure roller 11. The pressure roller 11 is provided with an elastic surface such as cork to keep the thread from slipping between rollers 10 and 11. The pressure roller is mounted on swing arms 12 (only one of which is shown) by which the rollers 10 and 11 may be manually moved apart for threading purposes. In order to distribute wear evenly over the surface of the rollers 10 and 11 a conventional low frequency traverse mechanism 13 is used, the structure of which is not shown. Beyond thread brake 14 and the traverse 13 the monofil engages the roller 11 for more than 180 in order further to mim'mize a tendency of the thread to slip.

The movement of the traversing thread guide 13 axially of the rollers 10 and 11 makes for even wear distribution across the surfaces of the rollers.

2,993,333 Patented July 25, 1961 ice The monofil, after leaving the surface of roller 10 is passed over a pair of tensioning rods 15 and wound about a drawing device 16 comprised of two rollers 16a, 16b rotating on convergent axes the larger of which, 16b, is driven with a peripheral velocity several times greater than that of the supply roller 10. Due to the convergent relation of the axes of the rollers 16a and 16b the monofil passes around them in a generally helical path of suflicient length to maintain the respective windings in spaced relationship. Any known means may be used for driving rollers 10, 16b at the desired speeds.

After leaving the drawing device 16, the monofil is led over a guide roller 17, through a tube 18, over rollers 19 and 20 and through a guide 21 to the traveler 22 of a twister ring 23. The ring 23 is mounted on a reciprocating rail 24 which reciprocates vertically in relation to a spindle 25 which is rotated about its own axis.

The tube 18 is provided with an electric resistance through which current is led by conductors 26 and 27. Thisftube has an internal diameter preferably not exceeding 1 mm., and on the order of 0.6 mm. in the modification shown.

The ring twister is entirely conventional and the heater is of the design shown in application Serial Number 562,337 filed January 30, 1956, owned in common herewith which has now matured to Patent No. 2,869,312, issued January 20, 1959. In an embodiment of the present invention which has proved to be very satisfactory in actual practice, yarn consisting of polycaprolactam traveling at a velocity of 190 m./min. is heated in a tube having a length of approximately 30 centimeters and maintained at a temperature of to 155 centigrade.

It is interesting to note that the heat which is applied to the yarn in the present instance must be dry heat. A heat treatment of multifilament polyamide yarns under conditions of humidity increases knitting difliculties and degrades the uniformity of the knit product. Moreover, the size of the opening in tube 18 is so nearly the same as the diameter of the yarn that small, low amplitude oscillations of the yarn incidental to its travel between rollers 17 and 19 will cause it to contact the inner wall of the tube intermittently in Very nearly all of its radii, as explained in said copending application Serial Number 562,337.

In a practical embodiment of the process according to the invention an undrawn and substantially untwisted monofil, with a denier of 70 and consisting of polycaprolactam, was first drawn between the roller 10 and the drawing device 16 to such an extent that the thread was lengthened 3.5 fold, and the denier thereof was inherently reduced. The thread thus drawn, left the drawing device 16 with a velocity of 19.0 m./min., thereafter was heated in the small tube 18 having a length of approximately 30 centimeters and which was kept at a temperature of 0., and finally, after passing through an air zone of 35 cm., was wound on the spindle 25. The traveller 22 of the ring spindle had such a weight that the thread could shrink about 4% before winding. Said shrinkage could of course have been adjusted to a diflerent value by using a different traveller, for instance one with a different weight.

The monofil thus obtained had a strength of approximately 500 g./ 100 denier and an elongation of 32%.

A set of spools, wound with these threads, was divided into two equal parts. The threads on the spools of one half of the set were then given an S-twist and those of the other half a Z-twist, and this in such a manner that the monofils finally possessed 450 S-turns and 450 Z- turns, respectively, per meter.

Next, a stocking was knitted from these threads, whereby alternately two rounds were knitted of S-twisted thread and two rounds were knitted with Z-twisted thread.

point of the polymer.

The stockings thus manufactured showed a strikingly smooth and regular knit, in which the vertical mesh rows ran in a zigzag line, as a result of which the stockings possessed a high elasticity.

It is evident, that within the scope of this invention, monofils with other deniersmay too be processed, whereby different drawing ratios and different heating temperatures may be applied. Likewise the twist of the threads may be chosen higher or lower, depending on the desired elasticity of the textiles.

It is understood that the phrase linear polycondensation produots applies not only to polyamides prepared from lactams, and from dicarboxylic acid and diamines, but also polyesters and polyurethanes. Of course, when applying the invention to threads consisting of other polymers than polyamides, the heating temperatures will have to be adjusted differently depending on the melting The correct temperatures though are easily determined by means of a few experiments.

What is claimed is:

1. A process for preparing twist lively thread of linear polycondensation products comprising the steps of continuously supplying undrawn and substantially untwisted monofilament thread of a given denier to a drawing zone, drawing said substantially untwisted thread to reduce the denier thereof, dry heating said drawn and substantially untwisted thread, cooling said drawn and substantially untwisted thread, collecting said drawn and substantially untwisted thread while imparting twist thereto, and there after further twisting said drawn and twisted monofilament thread to a twist lively condition.

2. A process as set forth in claim 1 wherein the second mentioned twisting operation increases the twist in said monofilament thread to a total twist in the neighborhood of about 450 turns per meter.

References Cited in the file of this patent UNITED STATES PATENTS 2,199,411 Lewis May 7, 1940 2,451,919 Clarkson Oct. 19, 1948 2,509,741 Miles May 30, 1950 2,728,973 Klm'lmel Ian. 3, 1956 2,803,108 Stoddard et a1 Aug. 20, 1957 2,813,393 Kingsbury et al. Nov. 19, 1957 

